How Much HP Do You Really Need???
02-11-2010, 02:34 PM
#27
Torque is referenced in this case to acceleration - which is wrong.
HP difference determines acceleration rates, not torque.
Much like the whole boost vs flow thing - torque is a static measurement of force while HP tells you what the engine is doing.
HP difference determines acceleration rates, not torque.
Much like the whole boost vs flow thing - torque is a static measurement of force while HP tells you what the engine is doing.
Last edited by Kane; 12-05-2010 at 07:21 AM.
02-11-2010, 02:38 PM
#28
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Because an engine putting out only 1ft lb of torque but can spin fast enough to generate 1,000HP will simply not have a very good acceleration rate. Stick it on a 3,000lb vehicle, and I would struggle to believe it would move the car at all (without gear reduction for a torque multiplier). Not enough torque? or Not enough HP difference?
02-11-2010, 02:51 PM
#31
When we tune on the dyno, we tune for torque.
The dyno computes horsepower for us and we go to great lengths to calculate out the effect of gearing.
The instantaneous torque at any RPM is like an integral in calculus - its an infinitely small slice of the overall curve of the motor. An instantaneous snapshot of the action of combustion at that moment.
We could tune for the "instantaneous" moment of power if we wanted to, but we would still be calculating, rather than measuring because we would be attempting to remove the value of time from the measurement - something we don't need to do with torque.
Once again, much like the boost vs. flow argument, I think people are over-thinking the "theory".
Just work practically - what metric gives us the most readily useful view of exactly what is going on at the exact, timeless snapshot that we are attempting to adjust?
The dyno computes horsepower for us and we go to great lengths to calculate out the effect of gearing.
The instantaneous torque at any RPM is like an integral in calculus - its an infinitely small slice of the overall curve of the motor. An instantaneous snapshot of the action of combustion at that moment.
We could tune for the "instantaneous" moment of power if we wanted to, but we would still be calculating, rather than measuring because we would be attempting to remove the value of time from the measurement - something we don't need to do with torque.
Once again, much like the boost vs. flow argument, I think people are over-thinking the "theory".
Just work practically - what metric gives us the most readily useful view of exactly what is going on at the exact, timeless snapshot that we are attempting to adjust?
02-11-2010, 02:53 PM
#33
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I think it is almost entirely semantics, personally. Everyone saying the same thing in a different way because they understand the same basis from a different perspective.
Important semantics though...
Important semantics though...
02-11-2010, 02:57 PM
#34
I know exactly what Jeff is saying and I am not disagreeing with him, though it's all style points.
The problem that I have is when people say "aw man we need more low end torque" - or "this car is slow because it lacks torque". As these are just silly ignorant statements; XYZ car is slow because it lacks power / a usable powerband - whatever. But the metric is power...not torque.
But ultimately yeah - most of us are saying the same thing, just from a different perspective.
The problem that I have is when people say "aw man we need more low end torque" - or "this car is slow because it lacks torque". As these are just silly ignorant statements; XYZ car is slow because it lacks power / a usable powerband - whatever. But the metric is power...not torque.
But ultimately yeah - most of us are saying the same thing, just from a different perspective.
02-11-2010, 03:06 PM
#35
Well, when they say "this car is slow because it lacks torque", it does need more "low-end torque"!
The problem is you can't feel torque because you exist in a space which is constrained by time.
You feel the power of acceleration, which is defined by time. So, in that instance, they are talking about power, even though it is defined by torque.
But, when you get that power, you are doing so by increasing torque.
The problem is you can't feel torque because you exist in a space which is constrained by time.
You feel the power of acceleration, which is defined by time. So, in that instance, they are talking about power, even though it is defined by torque.
But, when you get that power, you are doing so by increasing torque.
02-11-2010, 03:09 PM
#36
hey you guys - how about you quit messing about and give some useful advice over here ...
https://www.rx8club.com/showthread.p...27#post3427427
https://www.rx8club.com/showthread.p...27#post3427427
02-11-2010, 03:49 PM
#37
250 to 275 is perfect.
Can hall people and accerate on the freeway.
It's too bad all the HP is too much.
You either buy small HP or Bi HP.
They don't offer what's practicle.
Can hall people and accerate on the freeway.
It's too bad all the HP is too much.
You either buy small HP or Bi HP.
They don't offer what's practicle.
02-11-2010, 03:54 PM
#38
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hey you guys - how about you quit messing about and give some useful advice over here ...
https://www.rx8club.com/showthread.p...27#post3427427
https://www.rx8club.com/showthread.p...27#post3427427
As someone who has daily driven a car with 660rwhp I can say....it was too much. REALLY fun, but not much use other than burning up sets of BFGs and destroying rear ends, clutches and torque tubes.
All in all I would say MM has it right, about 9:1 is just perfect. My vette when it was cam and bolt ons was no less of a blast to drive than after I supercharged it.
And now my boosted Rx8 with 300+ feels just perfect. More than enough to put a smile on my face and easily enough to get into trouble
02-11-2010, 07:25 PM
#48
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